The invention relates generally to percutaneous transluminal coronary angioplasty (PTCA) in which a dilatation catheter is used to cross a lesion and dilate the lesion area to restore blood flow to the artery. More specifically, the invention relates to a catheter and stent assembly adapted to provide vibratory energy to assist in crossing and dilating calcified lesions.
In typical PTCA procedures, a guiding catheter having a pre-shaped distal tip is percutaneously introduced into the cardiovascular system of a patient and advanced therein until the pre-shaped distal tip thereof is disposed within the aorta adjacent to the ostium of the desired coronary artery. The guiding catheter is twisted or torqued from the proximal end to turn the distal tip of the guiding catheter so that it can be guided into the coronary ostium. A dilatation catheter having a balloon on its distal end and a guide wire slidably disposed within an inner lumen of the dilatation catheter are introduced into and advanced through the guiding catheter to its distal tip. The distal tip of the guide wire is usually manually shaped (i.e., curved) before the guidewire is introduced into the guiding catheter along with the dilatation catheter. The guide wire is first advanced out the distal tip of the guiding catheter, into the patient's coronary artery, and torque is applied to the proximal end of the guide wire, which extends out of the patient, to guide the curved or otherwise-shaped distal end of the guide wire as the guide wire is advanced within the coronary anatomy until the shaped distal end of the guide wire enters the desired artery. The advancement of the guide wire within the selected artery continues until its distal end crosses the lesion to be dilated. The dilatation catheter is then advanced out of the distal tip of the guiding catheter, over the previously advanced guide wire, until the balloon on the distal extremity of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated to a predetermined size with radiopaque liquid at relatively high pressures (e.g., 4-12 atmospheres) to dilate the stenosed region of the diseased artery. The balloon is then deflated so that the dilatation catheter can be removed from the dilated stenosis and blood flow can resume through the dilated artery.
Further details of guiding catheters, dilatation catheters, guide wires, and other devices for angioplasty procedures can be found in U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,439,185 (Lundquist); U.S. Pat. No. 4,468,224 (Enzmann et al.); U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,438,622 (Samson et al.); U.S. Pat. No. 4,554,929 (Samson et al.); U.S. Pat. No. 4,582,185 (Samson); U.S. Pat. No. 4,616,652 (Simpson); U.S. Pat. No. 4,638,805 (Powell); U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,898,577 (Badger et al.); and U.S. Pat. No. 4,827,943 (Taylor et al.), which are hereby incorporated herein in their entirety by reference thereto.
Several notable improvements have recently been made in balloon angioplasty catheters. One such modification, commonly referred to as a rapid-exchange catheter, is described in U.S. Pat. No. 4,748,982 (Horzewski et al.), wherein a short sleeve or inner lumen at least about 10 cm in length is provided within the distal section of the catheter body which extends from a first port proximal to the balloon to a second port in the distal end of the catheter and which is adapted to slidably receive a guide wire. The proximal port is not less than about 10 cm and not more than about 40 cm from the distal end of the catheter. Preferably, a slit is provided in the catheter body extending from the proximal port to a location proximal to the proximal end of the balloon to facilitate the removal of the catheter from the proximal end of the guide wire which extends out of the pattern.
Another modification, which was introduced into the marketplace by the assignee of the present application (Advanced Cardiovascular Systems, Inc.), has been perfusion-type dilatation catheters which allow for long-term dilatations to repair arterial dissections and other arterial damage. These perfusion catheters have a plurality of perfusion ports in the wall forming at least part of the catheter body proximal to the balloon which are in fluid communication with an inner lumen extending to the distal end of the catheter body. A plurality of perfusion ports are preferably provided in the catheter body distal to the balloon which are also in fluid communication with the inner lumen extending to the distal end of the catheter body. When the balloon on the distal extremity of the dilatation catheter is inflated to dilate a stenosis, oxygenated blood in the artery or the aorta or both, depending upon the location of the dilatation catheter within the coronary anatomy, is forced to pass through the proximal perfusion ports, through the inner lumen of the catheter body and out the distal perfusion ports. This provides oxygenated blood downstream from the inflated balloon to thereby prevent or minimize ischemic conditions in tissue distal to the catheter to thereby facilitate long-term dilatations. As a result, care should be exercised in sizing the perfusion ports and the inner lumen to ensure that there is adequate flow of oxygenated blood to tissue distal to the catheter to eliminate or minimize ischemic conditions. Commercially available perfusion catheters generally have relatively large profiles due to the size of the inner tubular member which extends through the interior of the balloon which prevents their use in many distal coronary locations.
A major and continual thrust of development work in the field of intravascular catheters, particularly coronary angioplasty catheters, has been to reduce the profile, i.e., transverse dimensions, of the aforementioned catheters and to improve the flexibility thereof without detrimentally affecting the pushability, particularly in the distal portion of such catheters. A reduction in profile with little or no loss in pushability allows a dilatation catheter to be advanced much further into a patient's coronary vasculature and to cross much tighter lesions.
While the foregoing methods and devices are suitable in most instances to perform a PTCA, especially the prior art low-profile catheters, there exists certain conditions which preclude or at least make PTCA procedures extremely difficult with the prior art devices. For example, when the stenosis (or lesion) in the coronary artery is a near total occlusion, or when the plaque is calcified and essentially blocking almost all blood flow, conventional guide wires and dilatation catheters are unable to cross the stenosis. Complications also can arise if the physician tries to force the guide wire or dilatation catheter through the plaque. Very often, plaque has only one opening through which blood flows, but there are a number of fissures in the plaque. If the physician tries to force the guide wire through a tight lesion, and instead the guide wire follows one of the fissures, then the artery might be perforated as the guide wire follows the fissure instead of the blood flow path. Assuming the guide wire and balloon can cross the stenosis, hard lesions may have calcium in them and typically will require very high balloon pressures to "crack" the lesion and restore blood flow.
Assuming the guide wire is able to cross a tight lesion, there is no guarantee the dilatation catheter will be able to cross, and even if it does cross, it may be difficult or dangerous to the patient to inflate the dilatation balloon at high pressures. The prior art devices offer no solution to this problem of tight lesions, other than to withdraw the guide wire and catheter and then consider alternative procedures such as cardiopulmonary bypass surgery. The present invention is designed to cross nearly occluded arteries and allow the balloon to dilate a calcified lesion more easily and at lower pressures.